Swimming is a popular competitive sport and, especially for athletes competing at the higher levels, significant investment is made to track their training and competitive races to collect data that can be used to monitor and help improve their performance.
There are also very many people that, although not participating at a competitive level, swim regularly to maintain or improve their fitness and general wellbeing. In the past, this type of swim ‘consumer’ has not been especially concerned with monitoring their performance. More recently, however, there has been a growing trend for consumers to measure and capture data around many aspects of their life, typically using a smartphone (sometimes in combination with ancillary motion sensors), especially for diet and fitness activities. Capturing such “personal metrics” enables a consumer to more easily understand their performance and seek to maintain or improve performance through the setting and tracking goals for their fitness activities.
Whilst developments in recent years now means there are a wide range of activity monitors available to the consumer for monitoring land-based activities (walking, running, cycling, etc), the development of activity monitors for water-based activities (swimming, water-aerobics, water-polo, underwater hockey, etc) has been less rapid, in part down to the unique challenges faced in capturing and recording data during water-based activities, especially the need to ensure that monitoring devices can function reliably when immersed in water.
One example of a known swim activity monitor is the Speedo Aquacoach™ watch. This waterproof watch can be worn by a swimmer in the pool and can be used to track laps, distance, speed and calories burned. It also detects swim stroke per lap utilising an inbuilt accelerometer. US2010-0030482 describes another example of a swim activity monitor. The monitor described in this document measures body orientation and forward speed with a three axis accelerometer (and optionally also a three axis gyroscope) that is worn by the swimmer on the small of their back, abdomen or head. This monitor provides real-time feedback to the swimmer via an earpiece or a swimming goggle with a digital display.
Another type of activity monitor that can be used during swimming is a multi-activity monitor. That is, a monitor that can operate to record multiple different type of activity (e.g. running, walking, cycling and swimming), such as the Fitbit™ activity trackers. Another example of a multi-activity monitor is described in US2012/0118084. The monitor described in this document records movement and automatically switches between a mode for operating in air and a mode for operating in water, i.e. swimming, using a sensor that determines when the monitor is in water.
One problem with known activity monitors, especially those using complex algorithms to determine, for example, different types of motion, is that the on-board processing of the algorithm quickly depletes a battery. This leads to monitors that are either bulky to incorporate high capacity batteries or that require fairly frequent changes of batteries (e.g. every 2 or 3 months) or frequent recharging. A compact swim monitor with a long battery life (for example, up to a year or more, would be desirable).